Study on one-dimensional consolidation of saturated soil with semi-pervious boundaries and under cyclic loading

The variation of effective stress ratio of stratfied soil with semi-pervious boundaries and under cyclic loading was analyzed on the basis of Terzagh's one-dimensional consolidation assumptions. A solution by Laplace Transform was obtained for the case when the soil was under time-varied loading. With numerical inversion of Laplace Transform, some useful results were obtained for several kinds of commonly encountered loadings. The results can be meaningful in engineering practice. Project supported by the National Natural Science Foundation of China (No. 59908012) and Fok Ying Tung Education Fundation (No. 81067), Education Ministry of China.     

GH4169合金高温多轴低周疲劳寿命预测

基于临界面模型的方法提出一个新的(修正的)多轴低周疲劳损伤准则.该准则与目前的临界面法所不同的是,在预测多轴低周疲劳寿命的模型中,同时考虑临界面上最大剪应变和正应变在不同加载路径下对多轴低周疲劳损伤的贡献。试验结果表明,本文提出的多轴低周疲劳寿命预测模型,对于GH4169合金高温多轴疲劳寿命估算具有较高的准确性。     

一种基于Matlab的大文本试飞数据绘图策略研究

为满足大文本试飞数据图形可视化分析需求,基于Matlab语言对大文本试飞数据的可视化绘图策略进行探讨。结合试飞数据绘图分析特点,重点研究大文本试飞数据绘图中的关键策略：①数据加载方式选择;②多参数对比曲线图绘制方法;③绘图操作的继承。通过关键绘图策略程序,减少了试飞数据载入内存时间,完成了3种多参数对比图绘制,达成重复绘图操作的有效继承。该关键策略可在大文本试飞数据可视化绘图分析中发挥关键作用,提高试飞数据绘图分析效率。     

超弹性形状记忆合金丝力学性能试验研究

超弹性是形状记忆合金（SMA）的重要特性之一。通过试验,研究了应变幅值和加卸载循环次数对SMA丝应力诱发马氏体相变应力、残余应变、最大相变应变和耗能能力的影响。研究结果表明,超弹性SMA丝具有良好力学性能,应变幅值对它的耗能能力具有较大的影响,循环次数的增加可使其力学性能更加稳定。     

运用等微增原理实现机组负荷优化分配

介绍了九江发电厂三期2×350MW机组运用等微增原理,根据各机组微增煤耗制定出机组负荷优化分配方案,以指导机组负荷优化分配,实现经济调度和经济运行。同时,对进一步细化和改进负荷优化分配系统和方案,全面体现效益最大化,提出了建议和措施。     

基于Jigsaw Proxy的加载网页的设计与实现

Jigsaw是W3C论坛的一个用Java语言实现的增强型Web服务器平台。它提供了HTTP方式的Proxy服务。通过对Jigsaw资源的配置不仅可以让Jigsaw成为一个代理服务器，而且还可以使代理服务器通过用户添加的动态扩展模块来实现附加功能。利用Jigsaw，将用户定义的Filter资源绑定在Frame上，在不改变原网页的结构的情况下，实现加载网页的功能，使得Jigsaw的适应范围更广，也更灵活。     

QFP结构中引脚焊缝界面端的奇异性热应力问题研究

由于引脚、印制电路板和焊接剂的热-机材料属性不同,在受到热载荷或机械载荷时,引脚焊接界面端会产生奇异性应力,有可能产生界面开裂。为了基于界面端奇异场来评价QFP结构引脚界面端力学行为,采用数值方法求解引脚焊缝任意角度尖劈界面端的应力强度系数。具体步骤为:首先,基于高次内插有限元特征分析法确定两相任意角度尖劈界面端的奇异性指数和应力角分布函数,并引入常数热应力项,获得热-机耦合奇异性应力场表达式;采用有限元分析技术和最小二乘拟合法来获得应力强度系数的数值解。考察了热-机材料属性对热载荷下焊接剂/印制电路板界面端应力强度系数的影响。结果表明:弹性模量、泊松比和材料热膨胀系数等均对应力强度系数有影响,适当的做出调整可以使界面端呈现良好的热应力状态。     

Athletics

The purpose of this study was to determine primary factors that contribute to the magnitude of the maximum torsional moment on the tibia during running based on information from three‐dimensional shank kinematics and ground reaction forces. Eight male subjects were asked to run along a straight track at 5.0 m s^‐1. Data were collected using two high‐speed cameras and a force platform. Each subject's left foot and tibia were modelled as a system of coupled rigid bodies. First, net axial moments acting at both ends of the tibia were calculated using inverse dynamics. Then the tibial torsional moment was determined from the quasi‐equilibrium balance of the net tibial axial moments. Our results showed considerable inter‐individual variations for the tibial torsional moment during the stance phase of running. The maximum torsional moment reflecting external rotational loading of the proximal tibia was significantly correlated with the outward tilt angle of the shank in the frontal plane (r = 0.78, p <0.05) and with the vertical force of ground reaction (r = 0.70, p <0.05). In conclusion, lowering tibial torsional loading by interventions based on the present findings may lead to the reduction of running injuries that occur in athletes’ tibiae.     

Stiffness,intralimb coordination,and joint modulation during a continuous vertical jump test

This study analysed the modulation of jump performance, vertical stiffness as well as joint and intralimb coordination throughout a 30-s vertical jump test. Twenty male athletes performed the test on a force plate while undergoing kinematic analysis. Jump height, power output, ground contact time, vertical stiffness, maximum knee and hip flexion angles, and coordination by continuous relative phase (CRP) were analysed. Analysis of variance was used to compare variables within deciles, and t-tests were used to compare CRP data between the initial and final jumps. Results showed reduction in jump height, power output, and vertical stiffness, with an increase in contact time found during the test. Maximum knee and hip flexion angles declined, but hip angle decreased earlier (10–20% of the test) than knee angle (90–100%). No changes were observed in CRP for thigh–leg coupling when comparing initial and final jumps, but the trunk–thigh coupling was more in-phase near the end of the test. We conclude that fatigue causes reduction in jump performance, as well as changes in stiffness and joint angles. Furthermore, changes in intralimb coordination appear at the last 10% of the test, suggesting a neuromotor mechanism to counterbalance the loss of muscle strength.     

冲击载荷作用下混凝土本构模型(英文)

为了更好地设计和分析混凝土结构,对冲击荷载作用下混凝土材料的力学特性进行了研究.将混凝土材料看成实体和微裂纹组成的复合材料,其中实体由粗骨料和水泥砂浆基体组成.假设水泥砂浆基体为弹性的、均匀的和各向同性的.基于Mori-Tanaka理论和Eshelby等效夹杂理论建立了冲击荷载作用下混凝土材料的动态本构模型.同时,进行了混凝土和水泥砂浆的冲击压缩试验.实验表明:混凝土和水泥砂浆都是率相关材料.在相同的冲击速度下,混凝土比水泥砂浆具有更高的承载能力,但混凝土的最大应变低于水泥砂浆材料.不论混凝土材料还是水泥砂浆材料,随着冲击速度的提高,破坏实验后试件的尺寸都逐渐减小.